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#ifndef MOZC_DICTIONARY_USER_POS_H_
#define MOZC_DICTIONARY_USER_POS_H_

#include <cstdint>
#include <iterator>
#include <string>
#include <utility>
#include <vector>

#include "base/port.h"
#include "base/serialized_string_array.h"
#include "data_manager/data_manager_interface.h"
#include "dictionary/user_pos_interface.h"
#include "absl/strings/string_view.h"

namespace mozc {
namespace dictionary {

// This implementation of UserPosInterface uses a sorted array of tokens to
// efficiently lookup required data.  There are two required data, string array
// and token array, which are generated by ./gen_user_pos_data.py.
//
// * Prerequisite
// Little endian is assumed.
//
// * Binary format
//
// ** String array
// All the strings, such as key and value suffixes, are serialized into one
// array using SerializedStringArray in such a way that array is sorted in
// ascending order.  In the token array (see below), every string is stored as
// an index to this array.
//
// ** Token array
//
// The token array is an array of 8 byte blocks each of which has the following
// layout:
//
// Token layout (8 bytes)
// +---------------------------------------+
// | POS index  (2 bytes)                  |
// + - - - - - - - - - - - - - - - - - - - +
// | Value suffix index (2 bytes)          |
// + - - - - - - - - - - - - - - - - - - - +
// | Key suffix index  (2 bytes)           |
// + - - - - - - - - - - - - - - - - - - - +
// | Conjugation ID (2 bytes)              |
// +---------------------------------------+
//
// The array is sorted in ascending order of POS index so that we can use binary
// search to lookup necessary information efficiently.  Note that there are
// tokens having the same POS index.
class UserPos : public UserPosInterface {
 public:
  static constexpr size_t kTokenByteLength = 8;

  class iterator
      : public std::iterator<std::random_access_iterator_tag, uint16_t> {
   public:
    iterator() = default;
    explicit iterator(const char *ptr) : ptr_(ptr) {}
    iterator(const iterator &x) = default;

    uint16_t pos_index() const {
      return *reinterpret_cast<const uint16_t *>(ptr_);
    }
    uint16_t value_suffix_index() const {
      return *reinterpret_cast<const uint16_t *>(ptr_ + 2);
    }
    uint16_t key_suffix_index() const {
      return *reinterpret_cast<const uint16_t *>(ptr_ + 4);
    }
    uint16_t conjugation_id() const {
      return *reinterpret_cast<const uint16_t *>(ptr_ + 6);
    }

    uint16_t operator*() const { return pos_index(); }

    void swap(iterator &x) {
      using std::swap;
      swap(ptr_, x.ptr_);
    }

    friend void swap(iterator &x, iterator &y) { x.swap(y); }

    iterator &operator++() {
      ptr_ += kTokenByteLength;
      return *this;
    }

    iterator operator++(int) {
      const char *tmp = ptr_;
      ptr_ += kTokenByteLength;
      return iterator(tmp);
    }

    iterator &operator--() {
      ptr_ -= kTokenByteLength;
      return *this;
    }

    iterator operator--(int) {
      const char *tmp = ptr_;
      ptr_ -= kTokenByteLength;
      return iterator(tmp);
    }

    iterator &operator+=(difference_type n) {
      ptr_ += n * kTokenByteLength;
      return *this;
    }

    iterator &operator-=(difference_type n) {
      ptr_ -= n * kTokenByteLength;
      return *this;
    }

    friend iterator operator+(iterator x, difference_type n) {
      return iterator(x.ptr_ + n * kTokenByteLength);
    }

    friend iterator operator+(difference_type n, iterator x) {
      return iterator(x.ptr_ + n * kTokenByteLength);
    }

    friend iterator operator-(iterator x, difference_type n) {
      return iterator(x.ptr_ - n * kTokenByteLength);
    }

    friend difference_type operator-(iterator x, iterator y) {
      return (x.ptr_ - y.ptr_) / kTokenByteLength;
    }

    friend bool operator==(iterator x, iterator y) { return x.ptr_ == y.ptr_; }
    friend bool operator!=(iterator x, iterator y) { return x.ptr_ != y.ptr_; }
    friend bool operator<(iterator x, iterator y) { return x.ptr_ < y.ptr_; }
    friend bool operator<=(iterator x, iterator y) { return x.ptr_ <= y.ptr_; }
    friend bool operator>(iterator x, iterator y) { return x.ptr_ > y.ptr_; }
    friend bool operator>=(iterator x, iterator y) { return x.ptr_ >= y.ptr_; }

   private:
    const char *ptr_ = nullptr;
  };

  using const_iterator = iterator;

  static std::unique_ptr<UserPos> CreateFromDataManager(
      const DataManagerInterface &manager);

  // Initializes the user pos from the given binary data.  The provided byte
  // data must outlive this instance.
  UserPos(absl::string_view token_array_data,
          absl::string_view string_array_data);
  ~UserPos() override;

  // Implementation of UserPosInterface.
  void GetPosList(std::vector<std::string> *pos_list) const override;
  bool IsValidPos(absl::string_view pos) const override;
  bool GetPosIds(absl::string_view pos, uint16_t *id) const override;
  bool GetTokens(absl::string_view key, absl::string_view value,
                 absl::string_view pos, absl::string_view locale,
                 std::vector<Token> *tokens) const override;

  iterator begin() const { return iterator(token_array_data_.data()); }
  iterator end() const {
    return iterator(token_array_data_.data() + token_array_data_.size());
  }

 private:
  absl::string_view token_array_data_;
  SerializedStringArray string_array_;

  DISALLOW_COPY_AND_ASSIGN(UserPos);
};

}  // namespace dictionary
}  // namespace mozc

#endif  // MOZC_DICTIONARY_USER_POS_H_
